From the viewpoint of space savings, flat panel displays such as liquid crystal displays, plasma displays, OLED displays, and field emission displays have recently become widespread instead of CRT displays that have been conventionally widespread. An additional thinning has been required for each of those flat panel displays. In particular, the OLED displays have been required not only to be easily portable by being folded or rolled but also to be usable in curved surfaces as well as flat surfaces. In addition, those requisitions to be usable in curved surfaces as well as flat surfaces are not limited to the displays. If solar cells or OLED lightings can be formed on the surfaces of substances each having a curved surface such as the surfaces of the bodies of automobiles, and the roofs, poles, and external walls of architectural structures, the solar cells or the OLED lightings will find use in an expanded variety of applications. Therefore, an additional thinning and high flexibility have been required for each of substrates and cover glasses used in those devices.
Luminescent materials used in the OLED displays deteriorate by contact with a gas such as oxygen. Therefore, a high gas barrier characteristic is required for a substrate used in the OLED displays, and hence the use of a glass substrate has been expected. However, glass used in the substrate is brittle to a tensile stress unlike a resin film, and hence has low flexibility. The concentration of a tensile strength to the surface of the glass substrate by the bending of the glass substrate leads to the breakage of the substrate. An ultra-thinning needs to be performed for imparting flexibility to the glass substrate, and such a glass film having a thickness of 200 μm or less as described in Patent Document 1 below has been proposed.
A glass substrate used in electronic devices such as a flat panel display or a solar cell is subjected to various treatments related to the production of the electronic devices such as a coating treatment with a transparent conductive film or the like, and a cleaning treatment. However, when the glass substrate used in those electronic devices is turned into a film, some degree of a change in stress leads to the breakage of the film because glass is a brittle material. Accordingly, there arises such a problem that it is remarkably difficult to handle the film upon performance of the above various treatments related to the production of the electronic devices.
In view of the foregoing, such a laminate of a glass sheet and a resin layer as described in Patent Document 2 has been proposed for improving the handleability of a glass film. Patent Document 2 describes a laminate obtained by providing the resin layer with an adhesive layer formed of an adhesive and the like, and then laminating a glass film. In such laminate, the glass film is supported by the resin film as a tough material, and hence the handling of the glass film laminate upon performance of the above various production-related treatments becomes easier than that in the case of the glass film alone.
However, upon handling of the laminate described in Patent Document 2, such a problem that a crack generates from an edge of the glass film and hence breaking, chipping, or the like occurs arises. An unnecessary portion generated during the forming of the glass film is cut and removed, and hence a fine flaw upon cut and removal of the unnecessary portion remains at the edge of the glass film. When a stress is concentrated to the edge of the glass film upon handling of the glass film, breaking, chipping, or the like occurs due to the fine flaw as an origin. The breaking, chipping, or the like cannot be prevented merely by laminating the resin layer on one surface of the glass film as described in Patent Document 2.
Citation List
Patent Document 1: JP-A-2008-133174
Patent Document 2: JP-A-2001-97733